FRUIT TREE PESTS.

Otago Witness, Issue 1825, 12 November 1886, Page 8

FRUIT TREE PESTS.

THE CODLIN MOTH. It is generally admitted that this destructive pest is known in some of our neighbourhoods, such as Akaroa and Nelson, although its presence has not yet been satisfactorily proved in Otago. But from "the immense quantity of fruit received into Dunedin from both these places as well as Tasmania, where its ravages have been noticeable for nearly 20 years, its appearance here at any time need not surprise anyone. As to be forewarned is to be forearmed, a description of the insect and its habits will place our readers in an advantageous position. Mr Fraser Crawford's description is very clear and minute as to its LIFE HISTORY. In early summer, the present time, when the young apple is just set, the moths, which have passed the winter either in larvse or pupze, emerge from their confinement, pair, and within 48 hours the females fly from apple to apple, depositing an egg in each, until they have exhausted their stock. In from seven to 10 days the larva is hatched, when it commences at once to gnaw a hole and bury itself in the substance of the fruit, making a burrow obliquely downwards so as to avoid the core. At this stage it is hardly visible to the naked eye. When six days old it measures nearly one-quarter of an inch and is about as thick as a silk thread. In 10 days it is about three-quarters of an inch long, and by the time it has burrowed about three-fourths of the distance to the core its presence may be known by the brown powder it throws out of the burrow. The body of tho young caterpillar is of a whitish colour and it has a black head. The next segment or

collar, as also the end segment, are darker in colour. It has eight little black dots or warts on each segment, so arranged as to make two rows down the back aud one row on each 6ide. From each dot proceeds a very fine white hair or bristle. The dots and hairs are only to be seen clearly with a magnifying glass. It has three pairs of true legs (legs with claws situated near the head), four pairs of ventral prolegs (legs without claws in the centre of the body), and one pair of prolegs at the anal extremity. This arrangement of legs is common to a great many kinds of caterpillars, but if a caterpillar is found insiile an apple or a pear it may sately be concluded that it is tbe

LARVA OF THE CODLIN MOTH. As it grows towards maturity, which it attains in about 20 days, the body becomes more or less of a pink or flesh colour, the dots nearly or quite disappear, and the head, collar, and anal segment become lighter in colour. In about 30 days' time the larva is prepared to leave the fruit. According to Californian authorities it then gnaws a hole through the apple, from which it lowers itself down by means of a silken thread either to the ground or to a branch. English authorities state that when about halfgrown it gnaws a hole to the outside for the purpose of expelling the pellets of excrement. It then returns to the centre of the apple, when it feeds at its ease. When within a few days of being full fed it enters the core and eats only the pip?, which causes the apple to fall. In South Australia it is found the larva adopts both methods. When an apple containing a caterpillar falls the little animal leaves the core, crawls along his breathing and cleaning gallery, the mouth of which it enlarges so as to permit of its

FREE PASSAGE INTO THE AIR. It now wanders about on the ground until it finds the 6tem of a tree, up which it climbs and hides itself under a piece of bark or in some convenient cranny. Newman says the fall of the apple, the exit of the grub, and his wandering to a place of security, usually takes place in the night time. In this situation he remains without stirring for a day or two, as if to rest himself after the uncommon fatigue of a two yards' march. The pupa or chrysalis is of a bright mahogany colour, and in from nine to 12 days it hplits open and the moth appears in all its beauty to commence its short life of six or seven clays ; or if the larva be one of the last brood, the change does not take place till after the winter is over and the young apples fit to receive the eggs. The moth is described by Wood as a

MOST EXQUISITELY COLOURED INSECT, but a magnifying glass and a good light are required to bring out all its beauties. The upper wings are rich brown, banded at the base and tip with a darker and warmer brown. In the dark band at the tip of the wing is an oval mark of brilliant gold-coloured scales, having a very dark centre. In certain lights this dark centre takes a reddish hue. Even the outer" wings when viewed in a side light shine as if made of the richest satin. By a proper adjustment of the light a rather curious effect can be produced, the wings of the one side glittering and shining in full splendour, while the corresponding wings of the other are nothing but dull grey, brown, and black.

THE PROBABLE RATE OF INCREASE is a question on which authorities differ. Some of the books on the subject speak of the moth as having but one generation in the year, while a Calif ornian official publication states positively that in the Sacramento Valley there are generally three broods. In Tasmania, according to some authorities, they have at least two, but this is disputed by othera who have given considerable attention to the subject. Mr Sherwin, of that colony, observes that this pest is likely to greatly reduce the value of the fruit industries of his island, and the best information on the subject is required to enable fruit growers to preserve their crops from its ravages.

THE REMEDIES RECOMMENDED are : Keeping the ground underneath the trees free from any vegetable growth and as smooth as possible, so as to afford no place of lodgment for the larvae ; scraping the stems of infected trees of all loose bark and burning it, and afterwards washing the stems with some chemicals, so as to destroy any larvas that may remain in the crannies; tying bands of cloth or paper round the stems, so as to trap the larvje, and gathering and destroying all apples or pears which have a grub hole mark.

THE DISTRIBUTION OF FRUIT TREE PESTS in the colonies is somewhat remarkable. In Otago we have neither the fusicladium or codlin moth to contend with, but in their stead we have the mussel scale and the mildew on our apples, which are unknown in South Australia, while that colony, on the other hand, suffers severely from the two first-named pests. There are others, again, which appear to have effected a lodgment all round, such as the American blight or woolly aphis, which is too well-known and easily seen to require any particular description. Then there is the

PEAR FHYTOPTTJS, which belongs to a most abnormal and exceptional group of mites, so much so as to constitute an entomological puzzle, and which was at first confused with the fusicladium in South Australia. It is extremely common about Dunedin, tbe difficulty being to find a pear tree absolutely free from it. Fortunately, its effects are not so highly injurious as most of the other pests. Still it is a pest, disfiguring the foliage, and must consequently affect the fruit. It may be seen in the earliest stages of the growth of the buds, as the very young leaves when still unfolding have often very small galls on them, which are of a pinkish colour. As the leaf expands, the brown blister-like spots are clearly seen. These are at first nearly round, but as they grow in size they spread laterally/generally taking the direction of the venation of tbe leaf. These are galls, for there is a decided thickening of the parenchyma, or inside^ portion of the leaf, and each of these contains a greater or lesser number of these mites. As these phytopti suok away the juices of the leaf or otherwise destroy the cellular tissue, it turns brown, and finally nearly dark. As the galls enlarge, owing to the food requirements of the population within, they often coalesce ; so that in time the greater portion of the leaf becomes a blackish scab, containing probably over 1000 phytopti. On examining a gall on the underside of the leaf, one and sometimes more little holes may be detected, through which tho inhabitants go forth to see the world. When a leaf is plucked and begins to wither, the mites generally leave the gall, and may be found scattered around. A powerful glass is, however, required, as a mite is about l-470th inch in length and l-630th in breadth. HORTICULTOB.